Batteries such as lithium ion secondary batteries are used in various fields, e.g., in vehicles such as a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle, household electric devices such as a notebook-sized personal computer, and industrial devices such an impact driver. One example of these batteries is known as a rectangular battery including an electrode body enclosed in a metal battery case having a rectangular parallelepiped outer shape, to be concrete, a rectangular battery in which a main body member having a bottom-closed rectangular cylindrical shape and a lid member inserted in an opening portion of the main body member, which are hermetically sealed by welding (see each figure of Patent Document 1). This Patent Document 1 discloses that an outer vessel (a main body member) is formed with projections at four opening corners in order to prevent dropping of a lid (a lid member) into the outer vessel.